1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus in which the position of scan is automatically corrected.
The present application is based upon Korean Application No. 97-33544, which is incorporated herein by reference.
2. Description of the Related Art
An image forming apparatus reproduces text or images on a recording medium according to text or image data signals. The image forming apparatus includes a photosensitive member, such as a photosensitive drum or photosensitive belt for forming an electrostatic latent image on a recording medium, a charging unit for charging the photosensitive member, an exposing unit for forming the electrostatic latent image by emitting light to the charged photosensitive member, a developing unit for forming a toner image by supplying a developer, such as a liquid toner, to the electrostatic latent image formed on the photosensitive member, and a transferring unit for transferring the toner image to the recording medium by heating and pressing the same.
FIG. 1 schematically shows the configuration of a conventional image forming apparatus having the above structure. Referring to FIG. 1, the conventional image forming apparatus includes a circulating photosensitive belt 100, onto which an electrostatic latent image is exposed by an exposing unit 110 and a toner image is developed by a developing unit 120. The exposing unit 110 is composed of laser scanning units (LSU) 110a, 110b, 110c, and 110d for each color. Of the LSUs, a Y-LSU 110a is an LSU for yellow, an M-LSU 110b is an LSU for magenta, a C-LSU 110c is an LSU for cyan, and a BK-LSU 110d is an LSU for black, The developing unit 120, having developing units 120a, 120b, 120c, and 120d for each color, performs development by applying a liquid toner on the electrostatic latent image formed by the exposing unit 110. When a toner image is formed on the photosensitive belt 100 by the developing unit 120, the image is printed on a print paper 150 by a transfer roller 130 and a heated press roller 140.
However, when scanning is performed by the respective LSUs 110a, 110b, 110c, and 110d for each color in the above image forming apparatus, misregistration occurs unless distances l.sub.1, l.sub.2 and l.sub.3 between each scanning position are equal. Thus, an initialization operation is performed to equalize the distances l.sub.1, l.sub.2 and l.sub.3 between the respective scanning positions on the photosensitive belt 100 of the image forming apparatus.
According to the conventional technology, in order to set the distances l.sub.1, l.sub.2 and l.sub.3 between the respective scanning positions on the photosensitive belt 100 to be equal, a test print is first performed and then an error is calculated by manually measuring the scanning positions for each color based on the printed image. Next, a lookup table is made with data of the generated errors and stored in a memory so that the scanning positions for each color are designated based on the stored data. However, since the initialization operation for the equalization of the distances between the scanning positions for each color is manually done in the conventional image forming apparatus, the initialization operation is performed inaccurately and takes a rather long time. Further, it is inconvenient to repeat such operation whenever the exposing unit is replaced.